The Public Switched Telephone Network (PSTN) in the United States, which has effectively provided service to business and the general public, is now facing new problems as it responds to consumer desires as the consumer adapts to new technologies. Among the changes impacting the industry are changes in usage habits of the end users. In the relatively recent past the operating telephone companies (Telco's) could reliably expect the user public to consistently use a one to two minute holding time for each telephone call completed through the network. This could then be relied upon to rate and engineer the network. At the same time it could be expected that the bandwidth needs of the subscriber public could be met by existing switch technology. Generally, this has comprised analog service through a line card or line unit (LU) and an end office switch. The analog voiceband channels (4 kHZ nominal) are digitized by the CODEC (coder/decoder) on the line card to create 64 kb/s DS level 0 (DS0) signals. Twenty-four of these DS0 channels from the CODECs are multiplexed by a channel bank to create a 1.544 Mb/s DS1 channel. A number of these DS1 channels are then digitally switched through the telecommunications network. The line card performs the analog to digital conversion at a sampling rate of 8,000 times a second. This is then sent over 64 kilobit per second (kb/s) time slots through the switch fabric and then on into the network for termination.
This plan and methodology provided relative stability for an extended period of time. The calls were 1-2 minute calls whose time of occurrence was subject to estimation. However in the last several years there has been exponential growth in use of the Internet, where the hold time may be measured in hours. In addition, modern public communication networks increasingly need to provide customers with a range of communication services, from baseband voice service, to computer data communications, to high speed digital data communications for multimedia and the like. Yet many such services are seriously impeded or virtually blocked by existing telephone network line cards. These provide coding and decoding (CODEC) functions between analog and digital signals, and process digital signals only at the relatively low, fixed bit rate.
It is now commonplace to use computers or PC's as a medium for voice communication over long distances via the PSTN and access to the Internet. However because of the coding function, the channel is still restricted by the 64 kb/s limitation at the line card or line unit. Regardless of the ultimate capabilities of exchange switches such as the AT&T (now Lucent) 5ESS, their limit for practical purposes is artificially restricted by present day network architecture and practices.
From the point of view of the local exchange carrier, data traffic creates a variety of problems.
For example, the long hold times tie up network resources. Also, the dialing patterns are not random. Large numbers of calls go through one or a small number of end offices to an Internet Service Provider's modem pool, placing an inordinate load on the terminating office and the trunks to that office. Reengineering the voice telephone network, just to meet the demand for added resources is already imposing heavy costs on local exchange carriers.
It is a primary object of the present invention to ameliorate these problems in the existing Public Switched Telephone Network.